| 摘要 |
PURPOSE:To prevent drift rotation by interrupting a speed feedback loop during halt of motor and controlling power conversion so that the field produced by an armature winding is fixed. CONSTITUTION:A PWM three-phase inverter comprises a current amplifier 4 for producing a variable frequency AC power supply from a DC power supply and feeding AC power to an AC synchronous servo motor 5. When a motor 5 is controlled through a speed regulator 1 and based on an external speed command Vs so that the actual speed Vi thereof matches with the speed command, a switch 10 is turned from side A to side B based on a latch signal 71a upon lowering of the rotational speed of the motor 5 below a predetermined level and a pole signal 6a is latched by means of the latch circuit 9. Consequently, a speed control loop is opened and a current command circuit 8a provides a command to a current control minor loop through the switch 10 so that a fixed phase current is fed to the motor thus fixing the rotor position and bringing the speed to zero. According to the invention, rotation due to drift of IC in the control circuit can be prevented. |
